The acting administrator of the Drug Enforcement Administration, Chuck Rosenberg, plans to step down this week, a law enforcement official familiar with his plans told CNN.
Rosenberg no longer wants to work in the Trump administration, the source said.
In July, after President Donald Trump told law enforcement officers in New York to be more "rough" with suspects, Rosenberg sent his employees an email that rebuked the President's suggestion.
"The President, in remarks delivered yesterday in New York, condoned police misconduct regarding the treatment of individuals placed under arrest by law enforcement," Rosenberg wrote in a message sent to DEA's "Global Distribution" list.
In the July email to employees, Rosenberg went on to say, "In writing to you, I seek to advance no political, partisan, or personal agenda. Nor do I believe that a special agent or task force officer of the DEA would mistreat a defendant. I know that you would not."
Rosenberg added: "So, why do I write? I write to offer a strong reaffirmation of the operating principles to which we, as law enforcement professionals, adhere. I write because we have an obligation to speak out when something is wrong. That's what law enforcement officers do. That's what you do. We fix stuff. At least, we try."